Transformer



UNITED STATiiS e ric.

VANNEVAR BUSH, F MEDFOBD, MASSACHUSETTS, ASSGNOR TO AMERCAN RAIDG & IRESMRCH CURPURATIN, DELAWARE.

TRNSF RMER.

inaaesc.

Specification of Letters atentF llatented Jui/ie 19230..

Application .led May 5, i317. Serial o. $6,721).

adapt them for voperation at different wavel connections, this alteration of the relation a like manner the relations lengths. As such apparatus has heretofore been arranged, this change has necessitated another adjustment to maintain constant th coeliicient of coupling between the primary and secondary. This adjustment has custoinarily consisted of a movement of these elements toward and from one another, so that as the number of turns in the second-ar i is decreased the primary and secondary are brought into cl oserproXimity, they being increased This is objectionable, in that while all the other adjustments required for a change of Wavelength may readily be 'obtained by a simple switching of electrical of the primary and secondary demands the bodily movement of one of these elements, an action which cannot easily or reliably'be accomplished' by mechanical connection with theswitching means. To depend upon an independent adjustment of the transformer elements throws an undesirable burden upon the operator. The 'present invention removes the difficulty by .providing 'a' trans-i former possessing a constant coefficient oi coupling for all adjustments of the length of its windings.

'In the accompanying draWings,'Figure lv shoivsia top plan view of oneembodiment of my invention; Fig. 2 is a side elevation thereof; Fig. 3 illustratesby a set of curves the relation between the radius of a primary Winding and thev coeiiicient of coupling for different numbers of turns ofthe secondary,

with the arrangement of transformer previo'usly used; Fig.v 4 shows for'a similarly arranged transformer'tlie relation betiveen the number of turns of secondary Winding and the coeilicient of coupling fortwo primaries of different radii; While Fig. 5 exhibits in i for a transformer. made in vaccordance 'with my in- Referring to Figs. l and Q., upon a suitable frame l0 is carried an insulating support, which in the form of invention l have chosen to illustrate is a disk il bearing radial arms l2 containing transverse slots 13 adapted to receive the spirally arranged turns of flat secondary AWinding consisting of a conducting ribbon la. Tapes l5 conneet the ends of the secondary and the delsired'number of intermediate points to cooperating apparatus,avhich is not shown.

The secondary is thus divided into sections., which may be made effective in various coinbinations to change the length ofthe ivinib ing and therefore itsinductance.

lv/lounted upon the frame l() opposite the secondary is an insulating spider i6, to the inner side of which is lined a dat primary 17 of any suitable number of turns of conductor. Clips or connectors i8 permit conductors 19 leading to the associated apparatus to be fixed to the primary at diliei'ent points so that the effective lengths of these portions noiv to be described may be varied. This primary l? consists of tivo main porn tions a. and Z), preferably in the forni of arcs of circles of Adifferent radii. a is smaller, lying between the inner turns of the secondary and its central turns, While b is situated between said central turns and the outer turns. The tivo arcuateportions are joined by a portion c which is generally radial, though its jiiiictures With the portions cand b are rounded as indicated at c to reduce the brush discharge. For use in some systems it may be desirable to furnish. sectional connections for changing the length of the primary, precisely as has been already described for the secondary.

To make clear the effect upon the coefficient of coupling of transformers provided with a singleturn primary of one radius of a change in the number of turns of the sec oiidary, fouricurves M, N, O and P are shown in Fig. 3, which are plotted with radii of the primaries as' ordinates and co efiicients of coupling as abscissae, the curves corresponding` respectively to sections of 10, 20, 30 and 4,0 'turns of secondary. It Will be seen that for a primary of any particular radius, the coe'iiicient of coupling varies considerably as the turns lof the secciidary are altered, requiring the adjustment of the dis Vtance between the primary and secondary as vpreviously pointed out. In Fig. 4l, the twol curves Q and R show the relations existing in the same type ot tre siniiner9 or that here tofore used, for two prifsaiies oft' three and seven inches radius respectively. these curves having `coeiticients ot coupling; as ordinates and turns ot secondary as ahscissee. ln the present embodiment ot the invention smaller nuini'ier of 'turns startat the inside o't the secondary winding and inet wordly, and it will he observed 'tnat v'the primary ot sino-ller radius displays o. nini-:iniiun coeiiicient coupling for the fewer 'turns of secondarye it decreasing as the nunibei' of turns of secondary increase, heceuse the added turns are farther removed troni the small primary. @t the large primary exactly the reverse is true, the coe@ font ot coupling` increasing as 'the turns t, second ary increase.

A consideration-of the curves in connection with that of Fig. will nialie apparent the theory underlying the ipv/sent invention. tit in each turn ot the primary there he provided portions of different radii, so that one portion will consist oll an'aic lying nearer the inner turns oi' the secondary and another portion oit the are in proximity to the outer turns ont the secondary., suoli un average inductive eii'ect Will ne obtained that the coefficient of coupling rnsy he made substantially the same for all the adjustments of the secondary. The structural tea.- tures ot a transformer so organized has already been explained in connection with Figs. l and 2f. rlie fir-cuate portions ci. and L of the primary 1"? hy their relation 'to the inner and outer turns ot the secti( nal sec-- ondary lll, give the novel results sought. The variation ot the lengths of the primary arcs by movements of the clips it? facilitate tho adjustment ot the transformer to give o coefiicient of coupling; constant in Value. The radii chosen 'tor the portions of and o correspond to those indicated hy the dotted lines in Fig. Curves similar in character to those ol" Fig. 4l plotted from observations inade upon such e coil are shown in Fig-'i'. 5. it will oe seen that the resultant curve appreaches closely to a. straight horizontal line5 ell ailiustinents of the turns of the secondary giving e coeiicient ot coupling about 0.37.

As it may he desired i" tie operaticn of the system in which the transformer is used to change the coe'liicient of coupling I.inde pendently ot' the alteration oi 'the 'turns oi the secondary, the spider iti has means niovingg the prnnsry toward and u the seconoary. ifhis is urnislie-:l .by journaled vto "Zi in the trarne l0 ai d hai/- ing it head 'oy 'which it may he turned. The inner end of the screw 2G is into 'the spider so that wijlen the s :re-o.-T is to ad troni ne from the 'traine n the spider arms pro s1 der end gn'iinatj'.

.1%. tianstorrner having o prinisry and secondi-try Winding, and means 'toi' Vary ingthe eifective length ot one ot' tusse windings, the other Winding being' constructed and arranged hy its coniorniiat-ioo to maintain. the coe'iicient oft coupling con-l stant hiring such vari .tion in length.

A. transformer hating a primary and a secondary, and nieans 'for 'varying the etn iiective nuinher ot turns in one of these eienients, the other element having portions differing; .in their relation to said turns whereby the coeticient oi'V coupling is moins tained constant upon a variation in 'i turns.

in a transtoriner. a Winding having each turn consisting ot :i Jlurality'ol por 1 port" an being) in e 'forni ot' an tions, eacl .i'luis ot which. is d ferent coin are the those out the assiiciati-d pensions7 f tornei cin cuit connections 'tot said portions, end means including said connections for Vary"- inej the eiie tive lengths ot the orcs.

o. transformer having a primary and secondary Winding. ineens for varying 'the effective length ot one winfflingg. 'the secon vinding consisting' ot orcs ol different radii in order to maintain 'the coei'ticieut ot coupi" substantially constant during vvaria tion. .in length of the .tiret Windin Signed at Boston7 in the county oi? tolk and @tate ot liiassaehusetts this 3d ot May, 193.7. i 

